Studies in detoxication. 67. The biosynthesis of the glucuronides of umbelliferone and 4-methylumbelliferone and their use in fluorimetric determination of β-glucuronidase

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Abstract
The glucuronides of umbelliferone and 4-methylumbelliferone were prepared by feeding these hydroxycoumarins to rabbits. The triacetyl methyl esters of the glucuronides were also described. The K salts of umbelliferone and 4-methylumbelliferone sulfuric esters were synthesized. These glucuronides are practically nonfluorescent, whereas the corresponding hydroxycoumarins are very highly fluorescent at pH 10-11, and can be measured fluorimetrically in quantities of 0.01 [mu]g/ml of less. 4-Methylumbelli-ferone glucuronide is easily prepared and can be used as a substrate for beta-glucuronidase. A fluorimetric method is described for the assay of this enzyme. The method is highly sensitive and is applicable to very small amounts of tissue or materials of low glucuronidase content.